Field of the Invention
The invention relates to an end closure of a superconductive electric cable which has at least one superconductive conductor which is surrounded by a tubular cryostat serving for guiding a cooling agent, and which is surrounded at its end by a housing containing a cooling agent through which an electrical connection to the outside is guided for its electrical connection (EP 1 617 537 B1).
Description of Related Art
A superconductive cable has at least one electrical conductor of a material which at sufficiently low temperatures changes over into the superconductive state. The electrical direct current resistance of an appropriately constructed conductor is zero at sufficiently low temperatures as long as a certain current i.e. the critical current, is not exceeded. Suitable materials are for example, oxidic materials on the basis of rare earths (ReBCO), particularly YBCO (yttrium-barium-copper oxide), or BSCCO (bismuth-strontium-calcium-copper oxide). Sufficiently low temperatures for bringing such a compound into the superconductive state are for example, between 67K and 110K. Another suitable material is, for example, magnesium diboride which at temperatures of approximately 39K or lower changes over into the superconductive state. Suitable cooling agents are, for example, nitrogen, helium, neon and hydrogen or mixtures of these materials.
When operating a superconductive cable, the cable is arranged in a cryostat through which one of the aforementioned cooling agents is conducted. A cryostat consists essentially of at least one thermally insulated pipe. In known technology, a cryostat has, for example, two pipes made of metal arranged concentrically relative to each other at a distance from each other with a vacuum insulation arranged between the two pipes. The cable is guided at the end of a transmission path to an end closure to which the cryostat is also connected. The at least one conductor of the superconductive conductor is at the end closure thereof subjected to a cooling agent. In addition, it is constructed for constructing an electrical connection by means of a passage from the end closure.
In accordance with the above mentioned EP 1 617 537 B1, the end closure includes a housing connected to a cryostat which surrounds the end of the superconductive conductor of a cable arranged in the cryostat. The superconductive conductor is connected to an electric conductor extending out of the housing surrounded by a pipe piece insulated by a vacuum insulation which is connected to the housing. The reference does not mention anything in connection with the construction of the housing.